People collect a wide variety of different items. However, when several people subjectively come to believe an item is interesting, sentimental, or valuable, it can become a collectible. Some collectibles become so popular that the market demand becomes the focus of a collector's craze. Often companies, selling mass-produced items, try to increase demand by advertising some “scarcity” of supply. Some label items as “Limited Editions,” for example, set specific production quantities, affix consecutive numbers, (1/1000, 2/1000, 3 of 1000, etc), list one specific manufacturing date, or announce one future retirement date for an entire series of collectible items.